Method for selective deposition of silicon nitride layer and structure including selectively-deposited silicon nitride layer

ABSTRACT

A method for selectively depositing silicon nitride on a first material relative to a second material is disclosed. An exemplary method includes treating the first material, and then selectively depositing a layer comprising silicon nitride on the second material relative to the first material. Exemplary methods can further include treating the deposited silicon nitride.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalPatent Application Ser. No. 62/815,820, filed Mar. 8, 2019 and entitled“METHOD FOR SELECTIVE DEPOSITION OF SILICON NITRIDE LAYER AND STRUCTUREINCLUDING SELECTIVELY-DEPOSITED SILICON NITRIDE LAYER,” which is herebyincorporated by reference.

FIELD OF INVENTION

The present disclosure generally relates to methods of forming thinfilms and to structures including the thin films. More particularly, thedisclosure relates to methods of forming structures that include asilicon nitride layer and to structures including such layers.

BACKGROUND OF THE DISCLOSURE

Features formed using silicon nitride films are used for a wide varietyof applications. For example, such features can be used as insulatingregions, as etch stop regions, and for etch-resistant protective regionsin the formation of electronic devices.

Typically, to form features including silicon nitride, a film of siliconnitride is deposited, the deposited film is then patterned using, forexample, photolithography, and then the film is etched to formed desiredfeatures including silicon nitride material. However, as device featurescontinue to decrease in size, it becomes increasingly difficult topattern and etch silicon nitride films to form features of desireddimensions. Additionally, lithography and etch steps can increase costsassociated with device manufacturing and increase an amount of timerequired for device fabrication.

Accordingly, improved methods for forming structures including siliconnitride films are desired.

SUMMARY OF THE DISCLOSURE

Various embodiments of the present disclosure relate to methods offorming features including silicon nitride and to the features includingsilicon nitride. While the ways in which various embodiments of thepresent disclosure address drawbacks of prior methods and structures arediscussed in more detail below, in general, various embodiments of thedisclosure provide improved methods of selectively depositing siliconnitride on one material on a substrate surface relative to anothermaterial on the substrate surface.

In accordance with at least one embodiment of the disclosure, a methodof forming a structure includes providing a substrate within a reactionchamber, the substrate comprising a surface comprising a first materialand a second material; treating the first material with a plasmatreatment; and selectively depositing a layer comprising silicon nitrideon the second material relative to the first material. The firstmaterial can include an oxide and the second material can comprise anitride. Exemplary oxides include Group IV oxides, such as siliconoxide, and metal oxides, such as titanium oxides. By way of example, theoxide can be or include (e.g., thermally-deposited) silicon oxide.Exemplary nitrides include Group IV nitrides, such as silicon nitride,and metal nitrides, such as titanium nitrides. By way of example, thenitride can be or include silicon nitride.

The step of selectively depositing a layer comprising silicon nitridecan include atomic layer deposition (ALD). Further, the step ofselectively depositing a layer comprising silicon nitride can be thermalor plasma enhanced. A temperature of a susceptor within the reactionchamber and/or a reaction chamber during the step of selectivelydepositing is between about 100° C. and about 500° C. or between about200° C. and about 400° C. A pressure within the reaction chamber canrange from about 0.5 to about 50 or about 5 to about 15 Torr. Exemplarymethods can further include a step of densifying the layer comprisingsilicon nitride—e.g., using a plasma treatment, wherein the plasma isformed using, for example, one or more noble gasses and helium.

In accordance with additional embodiments of the disclosure, a structureincludes a feature including silicon nitride. The feature can be formedusing methods as described herein. By way of particular example, afeature can include a self-aligned contact nitride layer formed using aselective deposition technique as described herein.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described herein above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught or suggested herein, withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein. These and other embodiments will become readilyapparent to those skilled in the art from the following detaileddescription of certain embodiments having reference to the figures, theinvention not being limited to any particular embodiment disclosed.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

A more complete understanding of exemplary embodiments of the presentdisclosure can be derived by referring to the detailed description andclaims when considered in connection with the following illustrativefigures.

FIG. 1 illustrates a method of forming a structure in accordance with atleast one embodiment of the disclosure.

FIG. 2 illustrates a structure in accordance with at least oneembodiment of the disclosure.

It will be appreciated that elements in the figures are illustrated forsimplicity and clarity and have not necessarily been drawn to scale. Forexample, the dimensions of some of the elements in the figures may beexaggerated relative to other elements to help improve understanding ofillustrated embodiments of the present disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Although certain embodiments and examples are disclosed below, it willbe understood by those in the art that the invention extends beyond thespecifically disclosed embodiments and/or uses of the invention andobvious modifications and equivalents thereof. Thus, it is intended thatthe scope of the invention disclosed should not be limited by theparticular disclosed embodiments described below.

As used herein, the term “substrate” may refer to any underlyingmaterial or materials that may be used to form, or upon which, a device,a circuit, or a film may be formed. A substrate can include a bulkmaterial, such as silicon (e.g., single-crystal silicon) and can includeone or more layers overlying the bulk material. Further, the substratecan include various topologies, such as recesses, lines, and the likeformed within or on at least a portion of a layer of the substrate.

As used herein, the term “cyclical deposition” may refer to thesequential introduction of precursors/reactants into a reaction chamberto deposit a layer over a substrate and includes processing techniquessuch as atomic layer deposition and cyclical chemical vapor deposition.

As used herein, the term “atomic layer deposition” (ALD) may refer to avapor deposition process in which deposition cycles, typically aplurality of consecutive deposition cycles, are conducted in a processchamber. Generally, during each cycle, a precursor is chemisorbed to adeposition surface (e.g., a substrate surface that can include apreviously deposited material from a previous ALD cycle or othermaterial), forming about a monolayer or sub-monolayer of material thatdoes not readily react with additional precursor (i.e., a self-limitingreaction). Thereafter, in some cases, a reactant (e.g., anotherprecursor or reaction gas) may subsequently be introduced into theprocess chamber for use in converting the chemisorbed precursor to thedesired material on the deposition surface. The reactant can be capableof further reaction with the precursor. Further, purging steps can alsobe utilized during each cycle to remove excess precursor from theprocess chamber and/or remove excess reactant and/or reaction byproductsfrom the process chamber after conversion of the chemisorbed precursor.The term atomic layer deposition, as used herein, is also meant toinclude processes designated by related terms, such as chemical vaporatomic layer deposition, atomic layer epitaxy (ALE), molecular beamepitaxy (MBE), gas source MBE, or organometallic MBE, and chemical beamepitaxy when performed with alternating pulses of precursor(s)/reactivegas(es), and purge (e.g., inert) gas(es).

As used herein, the term “cyclical chemical vapor deposition” may referto any process wherein a substrate is sequentially exposed to two ormore volatile precursors, which react and/or decompose on a substrate toproduce a desired deposition.

A layer including silicon nitride (SiN) can comprise, consistessentially of, or consist of silicon nitride material. Films consistingof silicon nitride can include an acceptable amount of impurities, suchas carbon, chlorine or other halogen, and/or hydrogen, that mayoriginate from one or more precursors used to deposit the siliconnitride layers. As used herein, SiN or silicon nitride refers to acompound that includes silicon and nitrogen. SiN can be represented asSiN_(x), where x varies from, for example, about 0.5 to about 2.0, wheresome Si—N bonds are formed. In some cases, x may vary from about 0.9 toabout 1.7, from about 1.0 to about 1.5, or from about 1.2 to about 1.4.In some embodiments, silicon nitride is formed where Si has an oxidationstate of +IV and the amount of nitride in the material may vary.

Turning now to the figures, FIG. 1 illustrates a method 100 of forming astructure in accordance with at least one embodiment of the disclosure.Method 100 includes the steps of providing a substrate within a reactionchamber, the substrate comprising a surface comprising a first materialand a second material (step 102), treating the first material with aplasma treatment (step 104), selectively depositing a layer comprisingsilicon nitride on the second material relative to the first material(step 106), and optionally densifying the layer comprising siliconnitride (step 108).

During step 102, a substrate is provided into a reaction chamber of areactor. In accordance with examples of the disclosure, the reactionchamber can form part of an atomic layer deposition (ALD) reactor.Exemplary single wafer reactors, suitable for use with method 100,include reactors designed specifically to perform ALD processes, whichare commercially available from ASM International NV (Almere, TheNetherlands). Exemplary suitable batch ALD reactors are alsocommercially available from ASM International NV. Various steps ofmethod 100 can be performed within a single reaction chamber or can beperformed in multiple reactor chambers, such as reaction chambers of acluster tool. Optionally, a reactor including the reaction chamber canbe provided with a heater to activate the reactions by elevating thetemperature of one or more of the substrate and/or thereactants/precursors.

During step 102, the substrate can be brought to a desired temperatureand pressure for step 104. By way of examples, a temperature (e.g., of asubstrate or a substrate support) within a reaction chamber can bebetween about 100° C. and about 500° C. or about 200° C. and about 400°C. A pressure within the reaction chamber can be about 0.5 to about 50or about 5 to about 15 Torr.

As noted above, the substrate provided during step 102 includes asurface comprising a first material and a second material. The firstmaterial can include an oxide and the second material can comprise anitride. Exemplary oxides include Group IV oxides, such as siliconoxide, and metal oxides, such as titanium oxides. By way of example, asilicon oxide can include thermally-deposited (e.g., carbon-doped)silicon oxide. Exemplary nitrides include Group IV nitrides, such assilicon nitride, and metal nitrides, such as titanium nitrides.

During step 104, the first material is exposed to a plasma treatment.The plasma treatment can create or change bonding states on the firstmaterial to inhibit deposition of silicon nitride on the first materialduring step 106. For example, the surface of the first material can bemodified to create or increase a nucleation delay of subsequent siliconnitride deposition.

In accordance with exemplary embodiments of the disclosure, the plasmafor the plasma treatment can be formed using a mixture of one or morenoble gasses (e.g., argon) and a gas comprising hydrogen (e.g., H₂). Aratio of the one or more noble gasses to gas comprising hydrogen canrange from, for example, about 0.1:1, about 1:0.1, 0.5:1, about 1:0.5,or about 1:1.

In some embodiments, the reaction chamber for step 104 may be configuredwith a capacitively coupled plasma (CCP) source, an inductively coupledplasma (ICP) source or a remote plasma (RP) source. A power used toproduce the plasma can range from about 150 to about 1000 W or about 400W to about 800 W. A time (e.g., a time of the activate plasma) for step104 can range from about 1 millisecond to about 5 minutes or about 1second to about 2 minutes.

When the first material includes an oxide, such as silicon oxide, it isthought that hydrogen active species created with the plasma generate ahigh density of —OH terminated sites on the oxide surface. The highdensity of —OH terminated sites, in turn, cause significant nucleationdelays for subsequent exposure to silicon nitride precursors andreactants. This allows for selective deposition on other surfaces.

During step 106, a layer comprising silicon nitride is selectivelydeposited on the second material relative to the first material. Anexemplary technique for selectively depositing silicon nitride on thefirst material relative to the second material includes a cyclicaldeposition process, such as an ALD process.

The same reaction chamber or separate reaction chambers can be utilizedfor steps 104 and 106. In embodiments where different reaction chambersare utilized for steps 104 and 106, the substrate may be transferredfrom a first reaction chamber (for treatment) to a second reactionchamber (for selective silicon nitride deposition) without exposure tothe ambient atmosphere. In other words, methods of the disclosure maycomprise treating the first material and selectively forming the siliconnitride film on the substrate in the same semiconductor processingapparatus. The semiconductor processing apparatus utilized for steps 104and 106 may comprise a cluster tool which comprises two or more reactionchambers and which may further comprise a transfer chamber through whichthe substrate may be transported between the first reaction chamber andthe second reaction chamber. In some embodiments, the environment withinthe transfer chamber may be controlled, i.e., the temperature, pressureand ambient gas can be controlled, such that the substrate, andparticularly the cyclical silicon nitride, are not exposed to theambient atmosphere.

One cyclic or ALD cycle may comprise exposing the substrate to a firstreactant (also referred to herein as a precursor), removing anyunreacted first reactant and reaction byproducts from the reaction spaceand exposing the substrate to a second reactant, followed by a secondremoval step. The first reactant may include, for example, a siliconhalide or other silicon source. Exemplary silicon halides includesilicon tetraiodide (SiI₄), silicon tetrabromide (SiBr₄), silicontetrachloride (SiCl₄), hexachlorodisilane (Si₂Cl₆), hexaiododisilane(Si₂I₆), octoiodotrisilane (Si₃I₈). The second reactant may comprise anitrogen source, such as nitrogen gas, ammonia (NH₃), hydrazine (N₂H₄)or an alkyl-hydrazine, wherein the alkyl-hydrazine may refer to aderivative of hydrazine which may comprise an alkyl functional group andmay also comprise additional functional groups. Non-limiting exampleembodiments of an alkyl-hydrazine may comprise at least one oftertbutylhydrazine (C₄H₉N₂H₃), methylhydrazine (CH₃NHNH₂) ordimethylhydrazine ((CH₃)₂N₂NH₂).

During the purge steps, precursors/reactants can be temporally separatedby inert gases, such as argon (Ar), nitrogen (N₂) or helium (He) and/ora vacuum pressure to prevent or mitigate gas-phase reactions betweenreactants and enable self-saturating surface reactions. In someembodiments, however, the substrate may be moved to separately contact afirst vapor phase reactant and a second vapor phase reactant. Becausethe reactions can self-saturate, strict temperature control of thesubstrates and precise dosage control of the precursors may not berequired. However, the substrate temperature is preferably such that anincident gas species does not condense into monolayers ormultimonolayers nor thermally decompose on the surface. Surpluschemicals and reaction byproducts, if any, are removed from thesubstrate surface, such as by purging the reaction space or by movingthe substrate, before the substrate is contacted with the next reactivechemical.

In some embodiments, exposing the substrate to a silicon halide sourcemay comprise pulsing the silicon precursor over the substrate for a timeperiod of between about 0.5 seconds and about 30 seconds, or betweenabout 0.5 seconds and about 10 seconds, or between about 0.5 seconds andabout 5 seconds. In addition, during the pulsing of the silicon halidesource over the substrate, the flow rate of the silicon halide sourcemay be less than 2000 sccm, or less than 1000 sccm, or less than 500sccm, or less than 250 sccm or even less than 100 sccm.

In some embodiments, exposing the substrate to the nitrogen source maycomprise pulsing the nitrogen source over the substrate for a timeperiod of between about 0.5 seconds to about 30 seconds, or betweenabout 0.5 seconds to about 10 seconds, or between about 0.5 seconds toabout 5 seconds. During the pulsing of the nitrogen source over thesubstrate, the flow rate of the nitrogen source may be less than 4000sccm, or less than 2000 sccm, or less than 1000 sccm, or even less than250 sccm.

The second vapor phase reactant comprising a nitrogen source may reactwith silicon-containing molecules left on the substrate surface. In someembodiments, the second phase nitrogen source may react with thesilicon-containing molecules left on the substrate surface to deposit acyclical silicon nitride film.

The cyclical deposition (e.g., ALD) process for selectively depositing alayer comprising silicon nitride may be repeated (loop 116) one or moretimes until the desired thickness of the cyclical silicon nitride isachieved. For example, the cyclical deposition process comprises formingthe cyclical silicon nitride film with a thickness of betweenapproximately 0.3 nm and approximately 30 nm.

Once an initial desired thickness of the silicon nitride film isdeposited, method 100 may proceed to step 108, densifying the layercomprising silicon nitride, in order to improve the materialcharacteristics (e.g., a wet etch rate in, for example, hydrofluoricacid and/or phosphoric acid) of the deposited silicon nitride film. Thesame reaction chamber or separate reaction chambers can be utilized fordeposition silicon nitride film and a step of exposing the layercomprising silicon nitride to a plasma treatment. If a separate reactionchamber, the two chambers can be part of a cluster tool as describedabove.

During step 108, a source gas from which the plasma is generated maycomprise one or more of nitrogen (N₂), helium (He), hydrogen (H₂) andargon (Ar). In particular embodiments of the disclosure, the source gasfrom which the plasma is generated may comprise a mixture of helium (He)and nitrogen (N₂) and the proportion of helium (He) gas to nitrogen (N₂)gas may be equal, i.e., 50% helium gas (He) to 50% nitrogen gas (N₂)(50:50). In alternate embodiments, the proportion of helium (He) gas tonitrogen (N₂) gas may be 10%:90%, or 20%:80%, or 30%:70%, or 40%:60%, or60%:40%, or 70%:30%, or 80%:20%, or 90%:10%, or any ranges therebetween.

In some embodiments of the disclosure, exposing the layer comprisingsilicon nitride to a plasma treatment may comprise applying a power tothe plasma source gas (es) of between about 150 W to about 1000 W orabout 400 W to about 800 W. The reaction chamber pressure can be lessthan 2 Torr or may even operate at a pressure of approximately 1 Torr,such as between about 0.1 Torr to about 10 Torr. In some embodiments,the substrate may be heated during the plasma treatment process to atemperature of greater than approximately 100° C., or to a temperatureof greater than approximately 200° C., or even to a temperature ofgreater than approximately 250° C., or to a temperature between about200° C. and about 600° C.

In some embodiments of the disclosure, exposing the silicon nitride filmto a plasma comprises exposing the silicon nitride to a plasma for atime period of less than approximately 300 seconds, or for a time periodof less than 150 seconds or even for a time period of less than 90seconds. In certain embodiments of the disclosure, the silicon nitridemay be exposed to the plasma treatment for a longer period of time, forexample, for a time period greater than 2 minutes, or greater than 5minutes, or even greater than 10 minutes. It should be noted that thelonger silicon nitride film is exposed to the plasma, the more likelythat the beneficial effects of the plasma treatment are to saturate;however, very long plasma exposure times may result in damage to thesilicon nitride film.

By way of particular example, a helium (He) and nitrogen (N₂) (50%:50%)gas plasma in a reaction chamber comprising a capacitively coupledplasma (CCP) source with a plasma power of 600 W, a substratetemperature of about 200° C. to about 600° C., and a reaction chamberpressure of 2 Torr for a time period of 90 seconds can be used to treatsilicon nitride.

Step 108 can be repeated (loop 110) or step 108 be performed after eachsilicon nitride deposition cycle or after a predetermined—e.g., two ormore—deposition cycles (loop 116). The deposition cycles (step 106) andplasma treatment steps (step 108) can be repeated a desired number oftimes (loop 112) until a desired thickness of the silicon nitride isobtained. Additionally or alternatively, steps 104-106 or 108 can berepeated (loop 114).

FIG. 2 illustrates a structure 200 in accordance with exemplaryembodiments of the disclosure. Structure 200 includes a substrate 202, afirst material 204, 208, a second material 206, and selectivelydeposited silicon nitride 210.

Substrate 202 can include any suitable material, such as semiconductormaterial and materials typically used to form semiconductor devices. Byway of example, substrate 202 can be or include silicon, other Group IVsemiconductor material, a Group III-V semiconductor, and/or a GroupII-VI semiconductor.

First material 204, 208 can include any of the first materials notedabove. For example, first material 204 and/or 208 can include an oxide,such as a Group IV or metal oxide. Second material 206 can include, forexample, a Group IV or metal nitride.

Silicon nitride 210 can be selectively deposited over (e.g., in directcontact with) second material 206 using a method as described herein.

The example embodiments of the disclosure described above do not limitthe scope of the invention, since these embodiments are merely examplesof the embodiments of the invention, which is defined by the appendedclaims and their legal equivalents. Any equivalent embodiments areintended to be within the scope of this invention. Indeed, variousmodifications of the disclosure, in addition to those shown anddescribed herein, such as alternative useful combinations of theelements described, may become apparent to those skilled in the art fromthe description. Such modifications and embodiments are also intended tofall within the scope of the appended claims.

What is claimed is:
 1. A method of forming a structure, the methodcomprising the steps of: providing a substrate within a reactionchamber, the substrate comprising a surface comprising a first materialand a second material, the first material comprising an oxide and thesecond material comprising a nitride; treating the first material with aplasma treatment; and selectively depositing a layer comprising siliconnitride on the second material relative to the first material.
 2. Themethod of claim 1, wherein the step of selectively depositing comprisesatomic layer deposition.
 3. The method of claim 1, wherein a temperatureof a susceptor within the reaction chamber during the step ofselectively depositing is between about 100° C. and about 500° C.
 4. Themethod of claim 1, wherein the step of treating comprises generating aplasma comprising noble gas species and hydrogen species.
 5. The methodof claim 4, wherein the noble gas comprises argon.
 6. The method ofclaim 4, wherein a source gas for the hydrogen species compriseshydrogen.
 7. The method of claim 1, wherein a plasma for the plasmatreatment is formed using a noble gas and a gas comprising hydrogen andwherein a ratio of the noble gas to gas comprising hydrogen ranges fromabout 0.1:1 to about 1:0.1.
 8. The method of claim 1, further comprisinga step of densifying the layer comprising silicon nitride.
 9. The methodof claim 8, wherein the step of densifying comprises exposing the layercomprising silicon nitride to a plasma comprising one or more noblegases.
 10. The method of claim 9, wherein the step of densifyingcomprises exposing the layer comprising silicon nitride to a plasmacomprising helium.
 11. The method of claim 10, wherein a ratio of argonto helium is between about 0.1:0.9 and about 0.9:0.1.
 12. The method ofclaim 1, wherein the first material comprises an oxide selected from thegroup consisting of a Group IV oxide and a metal oxide.
 13. The methodof claim 1, wherein the second material comprises a nitride selectedfrom the group consisting of a Group IV nitride and a metal nitride. 14.A structure formed according to the method of claim
 1. 15. The structureof claim 14 comprising a self-aligned contact nitride.
 16. The structureof claim 15 comprising the layer comprising silicon nitride overlyingand in contact with the self-aligned contact nitride.
 17. A method offorming a structure, the method comprising the steps of: providing asubstrate within a reaction chamber, the substrate comprising a surfacecomprising a first material and a second material, the first materialcomprising an oxide and the second material comprising a nitride;treating the first material with a plasma treatment formed using a noblegas and a gas comprising hydrogen; selectively depositing a layercomprising silicon nitride on the second material relative to the firstmaterial; and densifying the layer comprising silicon nitride.
 18. Themethod of claim 17, wherein the step of selectively depositing comprisesatomic layer deposition.
 19. A structure formed according to the methodof claim
 17. 20. The structure of claim 19 comprising a self-alignedcontact nitride.